Web　service　choreography　specifies　a　sequence　of　interactions　among　multiple　services.　How　to　test　if　a　Web　service　conforms　with　given　choreography　specification　is　a　challenging　question.　It　is　important　to　generate　test　data　(i.e.　XML　instance)　based　on　the　choreography.　Since　choreography　scenarios　describe　expected　interactions　among　multiple　participants,　it　is　possible　to　generate　test　data　based　on　those　scenarios.　This　paper　presents　a　set　of　test　data　generating　rules　and　algorithms　based　on　refined　type　trees,　which　are　obtained　from　choreography　scenario　and　corresponding　XML　Schema　type　document.　We　have　built　a　prototype　tool　to　support　automatic　test　data　generation　and　illustrate　the　process　of　generating　XML　instances　via　a　purchase　order　choreography　scenario　example.　Copyright　©　2014　by　The　Institute　of　Electrical　and　Electronics　Engineers,　Inc.